I've double checked the connections, no problem found. My newer M103 does not have an "engine temp sensor" -- MB calls it an ACC temperature sensor, and the parts page incorrectly states that it's located on the intake manifold when in fact it's on the rear of the head.
This sensor turns aux fans on high when 105c is reached, and cuts out ACC altogether when 115c is reached. Here's a pic:
The older 103's had a 3 pole green terminal that ran thru chassis #-A-079037 and had the same function as my 2 pole blue sensor. It is called an "engine temp sensor", so I'm assuming this newer 2 pole blue is my "engine temp sensor". My chassis # is B-399221.
Any other thoughts/solutions are appreciated!
'91 300E, 212K miles